12,382 research outputs found
The Origin of Radio Emission in Low-Luminosity Active Galactic Nuclei: Jets, Accretion Flows, or Both?
The low-luminosity active galactic nuclei in NGC 3147, NGC 4203, and NGC 4579
have been imaged at four frequencies with the Very Long Baseline Array. The
galaxies are unresolved at all frequencies, with size upper limits of
times the Schwarzschild radii of their central massive black holes.
The spectral indices between 1.7 and 5.0 GHz range from 0.2 to 0.4; one and
possibly two of the galaxies show spectral turnovers between 5.0 and 8.4 GHz.
The high brightness temperatures ( K) and relatively straight spectra
imply that free-free emission and/or absorption cannot account for the slightly
inverted spectra. Although the radio properties of the cores superficially
resemble predictions for advection-dominated accretion flows, the radio
luminosities are too high compared to the X-ray luminosities. We suggest that
the bulk of the radio emission is generated by a compact radio jet, which may
coexist with a low radiative efficiency accretion flow.Comment: To appear in ApJ (Letters). 4 page
Input-output relations at dispersing and absorbing planar multilayers for the quantized electromagnetic field containing evanescent components
By using the Green-function concept of quantization of the electromagnetic
field in dispersing and absorbing media, the quantized field in the presence of
a dispersing and absorbing dielectric multilayer plate is studied.
Three-dimensional input-output relations are derived for both amplitude
operators in the -space and the field operators in the coordinate
space. The conditions are discussed, under which the input-output relations can
be expressed in terms of bosonic operators. The theory applies to both
(effectively) free fields and fields, created by active atomic sources inside
and/or outside the plate, including also evanescent-field components.Comment: 14 pages, 1 figur
Aspects of U-duality in BLG models with Lorentzian metric 3-algebras
In our previous paper, it was shown that BLG model based on a Lorentzian
metric 3-algebra gives Dp-brane action whose worldvolume is compactified on
torus T^d (d=p-2). Here the 3-algebra was a generalized one with d+1 pairs of
Lorentzian metric generators and expressed in terms of a loop algebra with
central extensions. In this paper, we derive the precise relation between the
coupling constant of the super Yang-Mills, the moduli of T^d and some R-R flux
with VEV's of ghost fields associated with Lorentzian metric generators. In
particular, for d=1, we derive the Yang-Mills action with theta term and show
that SL(2,Z) Montonen-Olive duality is realized as the rotation of two VEV's.
Furthermore, some moduli parameters such as NS-NS 2-form flux are identified as
the deformation parameters of the 3-algebras. By combining them, we recover
most of the moduli parameters which are required by U-duality symmetry.Comment: 27 pages, v2: minor correction
Heisenberg quantization for the systems of identical particles and the Pauli exclusion principle in noncommutative spaces
We study the Heisenberg quantization for the systems of identical particles
in noncommtative spaces. We get fermions and bosons as a special cases of our
argument, in the same way as commutative case and therefore we conclude that
the Pauli exclusion principle is also valid in noncommutative spaces.Comment: 8 pages, 1 figur
Properties of Active Galaxies Deduced from H I Observations
We completed a new survey for H I emission for a large, well-defined sample
of 154 nearby (z < 0.1) galaxies with type 1 AGNs. We make use of the extensive
database presented in a companion paper to perform a comprehensive appraisal of
the cold gas content in active galaxies and to seek new strategies to
investigate the global properties of the host galaxies and their relationship
to their central black holes (BHs). We show that the BH mass obeys a strong,
roughly linear relation with the host galaxy's dynamical mass. BH mass follows
a looser, though still highly significant, correlation with the maximum
rotation velocity of the galaxy, as expected from the known scaling between
rotation velocity and central velocity dispersion. Neither of these H I-based
correlations is as tight as the more familiar relations between BH mass and
bulge luminosity or velocity dispersion, but they offer the advantage of being
insensitive to the glare of the nucleus and therefore are promising new tools
for probing the host galaxies of both nearby and distant AGNs. We present
evidence for substantial ongoing BH growth in the most actively accreting AGNs.
In these nearby systems, BH growth appears to be delayed with respect to the
assembly of the host galaxy but otherwise has left no detectable perturbation
to its mass-to-light ratio or its global gas content. The host galaxies of type
1 AGNs, including those luminous enough to qualify as quasars, are generally
gas-rich systems, possessing a cold interstellar medium reservoir at least as
abundant as that in inactive galaxies of the same morphological type. This
calls into question current implementations of AGN feedback in models of galaxy
formation that predict strong cold gas depletion in unobscured AGNs. (Abridged)Comment: To appear in ApJ; 14 page
Macroscopic dynamics of a trapped Bose-Einstein condensate in the presence of 1D and 2D optical lattices
The hydrodynamic equations of superfluids for a weakly interacting Bose gas
are generalized to include the effects of periodic optical potentials produced
by stationary laser beams. The new equations are characterized by a
renormalized interaction coupling constant and by an effective mass accounting
for the inertia of the system along the laser direction. For large laser
intensities the effective mass is directly related to the tunneling rate
between two consecutive wells. The predictions for the frequencies of the
collective modes of a condensate confined by a magnetic harmonic trap are
discussed for both 1D and 2D optical lattices and compared with recent
experimental data.Comment: 4 pages, 2 postscript figure
Branes from a non-Abelian (2,0) tensor multiplet with 3-algebra
In this paper, we study the equations of motion for non-Abelian N=(2,0)
tensor multiplets in six dimensions, which were recently proposed by Lambert
and Papageorgakis. Some equations are regarded as constraint equations. We
employ a loop extension of the Lorentzian three-algebra (3-algebra) and examine
the equations of motion around various solutions of the constraint equations.
The resultant equations take forms that allow Lagrangian descriptions. We find
various (5+d)-dimensional Lagrangians and investigate the relation between them
from the viewpoint of M-theory duality.Comment: 44+1 pages, reference added, typos corrected, and several discussions
added; v3, reference added, many typos corrected, the language improved; v4,
some typos and references corrected, final version to appear in J. Phys.
Is the brick-wall model unstable for a rotating background?
The stability of the brick wall model is analyzed in a rotating background.
It is shown that in the Kerr background without horizon but with an inner
boundary a scalar field has complex-frequency modes and that, however, the
imaginary part of the complex frequency can be small enough compared with the
Hawking temperature if the inner boundary is sufficiently close to the horizon,
say at a proper altitude of Planck scale. Hence, the time scale of the
instability due to the complex frequencies is much longer than the relaxation
time scale of the thermal state with the Hawking temperature. Since ambient
fields should settle in the thermal state in the latter time scale, the
instability is not so catastrophic. Thus, the brick wall model is well defined
even in a rotating background if the inner boundary is sufficiently close to
the horizon.Comment: Latex, 17 pages, 1 figure, accepted for publication in Phys. Rev.
Retaining Expression on De-identified Faces
© Springer International Publishing AG 2017The extensive use of video surveillance along with advances in face recognition has ignited concerns about the privacy of the people identifiable in the recorded documents. A face de-identification algorithm, named k-Same, has been proposed by prior research and guarantees to thwart face recognition software. However, like many previous attempts in face de-identification, kSame fails to preserve the utility such as gender and expression of the original data. To overcome this, a new algorithm is proposed here to preserve data utility as well as protect privacy. In terms of utility preservation, this new algorithm is capable of preserving not only the category of the facial expression (e.g., happy or sad) but also the intensity of the expression. This new algorithm for face de-identification possesses a great potential especially with real-world images and videos as each facial expression in real life is a continuous motion consisting of images of the same expression with various degrees of intensity.Peer reviewe
What Powers the Compact Radio Emission in Nearby Elliptical and S0 Galaxies?
Many nearby early-type (elliptical and S0) galaxies contain weak
(milli-Jansky level) nuclear radio sources on scales a few hundred parsecs or
less. The origin of the radio emission, however, has remained unclear,
especially in volume-limited samples that select intrinsically less luminous
galaxies. Both active galactic nuclei and nuclear star formation have been
suggested as possible mechanisms for producing the radio emission. This paper
utilizes optical spectroscopic information to address this issue. A substantial
fraction of the early-type galaxies surveyed with the Very Large Array by
Wrobel & Heeschen (1991) exhibits detectable optical emission lines in their
nuclei down to very sensitive limits. Comparison of the observed radio
continuum power with that expected from the thermal gas traced by the optical
emission lines implies that the bulk of the radio emission is nonthermal. Both
the incidence and the strength of optical line emission correlate with the
radio power. At a fixed line luminosity, ellipticals have stronger radio cores
than S0s. The relation between radio power and line emission observed in this
sample is consistent with the low-luminosity extension of similar relations
seen in classical radio galaxies and luminous Seyfert nuclei. A plausible
interpretation of this result is that the weak nuclear sources in nearby
early-type galaxies are the low-luminosity counterparts of more powerful AGNs.
The spectroscopic evidence supports this picture. Most of the emission-line
objects are optically classified as Seyfert nuclei or low-ionization nuclear
emission-line regions (LINERs), the majority of which are likely to be
accretion-powered sources.Comment: LaTex, 16 pages including embedded figures. Accepted for publication
in the Astrophysical Journa
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